The Style Sheet library section is used to apply custom CSS to ProtoShare components. You can do so by either adding/modifying classes or using an id selector.

Classes and ids can be seen under the Mark-up section of the properties panel.

Mark-up.png (8.01 KiB) Viewed 5753 times

In this example, the #id has been set to Submit so that styles can be assigned to this specific component.

To change the appearance of the button in question, the following CSS was added to the Style Sheet. You'll notice the addition of .s9-body, which is recommended to ensure that the CSS gets applied correctly.